Digital detectors are being increasingly used for medical X-ray imaging. Digital flat X-ray detectors based on amorphous silicon are in widespread use. Photoelements which allow signals to be produced on a detector-element basis are formed in the amorphous silicon. A layer of cesium iodide is applied as a scintillator to the amorphous silicon chip and converts X-ray light that is incident on the detector to visible light for the photoelements on the amorphous silicon chip.
CMOS technologies would allow a range of improvements in comparison to chips composed of amorphous silicon. For example, amplifiers could be provided on the detector element to improve the signal-to-noise ratio. Automatic dose measurement (AEC, Automatic Exposure Control) can be integrated on the chip, and the detectors may be counting detectors.
However, CMOS technology also has the disadvantage that, on an area basis, it is very expensive. The known cost reduction in the case of computer chips is due to the fact that the chips are becoming ever smaller. However, the size of flat X-ray detectors is governed by the area of the organs to be imaged by the X-ray technique (thorax, skull, etc.). The intrinsic requirement would be for a large-area CMOS detector with an area of 43×43 cm2. However, the largest areas of the most modern systems nowadays do not achieve wafer diameters of more than about 30 cm (12 inches), so that the maximum possible square area is somewhat more than 20×20 cm2.
It is thus intrinsically not possible to use CMOS-based flat detectors from the prior art.